Force balanced reciprocating valve

ABSTRACT

A device for generating pressure pulses includes a valve member disposed in a fluid passageway, the fluid passageway including a restriction, the valve member movable by an actuator relative to the restriction to generate a pressure pulse in a fluid in the fluid passageway based on varying a relative position between the valve member and the restriction and creating a differential pressure across the fluid passageway, the differential pressure applying a first force on the valve member. The device also includes a piston member in hydraulic communication with the differential pressure, the differential pressure applying a second force on the piston member, the piston member having a locomotive mechanical connection to the valve member.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of an earlier filing date from U.S.Provisional Application Ser. No. 62/870,261 filed Jul. 3, 2019, theentire disclosure of which is incorporated herein by reference.

BACKGROUND

In the resource recovery industry, various downhole tools are employedfor purposes such as flow control, drilling, directional drilling andformation property measurements. Examples of such tools includelogging-while-drilling (LWD) and measurement-while-drilling (MWD) tools.Communication between tools and/or between tools and the surface can beaccomplished using various telemetry systems.

One type of telemetry is mud pulse telemetry, which involvestransmitting communications via pressure pulses in borehole fluid, suchas drilling mud. Typically, downhole data is encoded into a digitalformat and pressure pulses are transmitted from a pulser to a receiver.

SUMMARY

An embodiment of a device for generating pressure pulses includes avalve member disposed in a fluid passageway, the fluid passagewayincluding a restriction, the valve member movable by an actuatorrelative to the restriction to generate a pressure pulse in a fluid inthe fluid passageway based on varying a relative position between thevalve member and the restriction and creating a differential pressureacross the fluid passageway, the differential pressure applying a firstforce on the valve member. The device also includes a piston member inhydraulic communication with the differential pressure, the differentialpressure applying a second force on the piston member, the piston memberhaving a locomotive mechanical connection to the valve member.

An embodiment of a method of generating pressure pulses includesreceiving a communication at a processing device, the processing deviceconfigured to control a communication module including a valve memberand a restriction disposed in a fluid passageway, controlling, by anactuator, movement of the valve member relative to the restriction togenerate pressure pulses in a fluid in the passageway based on varying arelative position between the valve member and the restriction andcreating a differential pressure across the passageway, the differentialpressure applying a first force on the valve member, and transmittingthe pressure pulses through the fluid to a receiver. The communicationmodule includes a piston member in hydraulic communication with thedifferential pressure, the differential pressure applying a second forceon the piston member, the piston member having a locomotive mechanicalconnection to the valve member.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 depicts an embodiment of a system for performing an energyindustry operation, the system including a communication moduleconfigured for mud pulse telemetry;

FIG. 2 depicts an embodiment of the communication module of FIG. 1 ;

FIG. 3 depicts aspects of an embodiment of a communication moduleincluding a pulser assembly and a force balancing assembly;

FIG. 4 depicts an embodiment of a force balancing assembly;

FIG. 5 depicts the pulser assembly and the force balancing assembly ofFIG. 3 in a closed position;

FIG. 6 depicts the pulser assembly and the force balancing assembly ofFIG. 3 in an open position;

FIG. 7 is a flow chart depicting an embodiment of a method ofcommunicating using a telemetry device;

FIG. 8 is a graph showing a relationship between valve force and valvemember position;

FIG. 9 is a graph showing a relationship between fluid pressure andvalve member position;

FIG. 10 illustrates fluid pressures exerted on a valve member operatedaccording to a selected stroke length;

FIG. 11 illustrates valve forces exerted on the valve member operatedaccording to the selected stroke length of FIG. 10 ;

FIGS. 12A and 12B (collectively referred to as FIG. 12 ) illustratefluid pressure and valve forces corresponding to an example of aselected stroke length;

FIG. 13 depicts effects of a force balancing assembly on valve force ona valve member;

FIG. 14 depicts effects of a force balancing assembly on valve force ona valve member;

FIG. 15 depicts an example of mechanical power provided by an actuatoron a prior art mud pulse telemetry valve member;

FIG. 16 depicts mechanical power provided by the actuator of FIG. 15when coupled to a force balancing assembly;

FIG. 17 depicts an example of inertial power as a function of strokelength;

FIG. 18 depicts an example of an encoded mud pulse telemetry pressuresignal with a sinusoidal stroke;

FIG. 19 depicts an example of an encoded mud pulse telemetry valveposition; and

FIG. 20 depicts inertia power demand according to the valve positioncurve of FIG. 19 .

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the figures.

Disclosed are devices, systems and methods for generating fluid pressuresignals and communicating via mud pulse telemetry. An embodiment of atelemetry device includes a valve member moveable relative to arestriction in a fluid passageway to generate fluid pulses. Fluid pulsesare generated by moving the valve member in an oscillating manner tocreate pressure differentials that are transmitted through boreholefluid to a receiver. The telemetry device also includes a forcebalancing assembly configured to use fluid pressure to counteract valveforces exerted on the valve member by the pressure differentials.

In one embodiment, the force balancing assembly includes a secondarymember (e.g., a piston member) in pressure communication with the fluidpassageway. The force balancing assembly includes a locomotivemechanical connection between the valve member and the secondary memberthat transmits forces on the secondary member to the valve member. Thetransmitted force at least partially cancels out the valve forces,allowing the valve member to be actuated with lower mechanical powerthan would be needed without the force balancing assembly.

Embodiments described herein provide a number of advantages andtechnical effects. Embodiments allow telemetry devices to be actuatedwith significantly less actuation force by balancing the hydraulicforces on the valve member. With hydraulic forces being reduced orcanceled, the required power to drive the valve member is significantlyreduced. Embodiments described herein allow for the realization of aplunger valve for high data rate mud pulse telemetry, maintaining thebenefits of the plunger valve with respect to lost circulation material(LCM) capability, plugging resistance and wide flow range adaptivity athigh signal strength (pulse pressure).

Hydraulically assisted pilot (or servo) valves are typically notactively position controlled and might have issues with plugging,sedimentation or wear in the pilot valve section. Lab and field testingof plunger valves demonstrate their advantages over rotary valves interms of ruggedness, flow and density spread, and plugging resistance.The embodiments described herein feature the advantages of plunger valveconfigurations while maintaining capability for high speed mud pulsetelemetry.

FIG. 1 shows an embodiment of a system 10 for performing an energyindustry operation (e.g., drilling, measurement, stimulation, wellconstruction, well completion and/or production). The system 10 includesa borehole string 12 that is shown disposed in a well or borehole 14that is drilled to penetrate at least one resource bearing formation 16during a drilling or other downhole operation. As described herein,“borehole” or “wellbore” refers to a hole that makes up all or part of adrilled well. It is noted that the borehole 14 may include vertical,deviated and/or horizontal sections, and may follow any suitable ordesired path. As described herein, “formations” refer to the variousfeatures and materials that may be encountered in a subsurfaceenvironment and surround the borehole 14.

The borehole string 12 is operably connected to a surface structure orsurface equipment such as a drill rig 18, which includes or is connectedto various components such as a surface drive or rotary table forsupporting the borehole string 12, rotating the borehole string 12 andlowering string sections or other downhole components. In oneembodiment, the borehole string 12 is a drill string including one ormore drill pipe sections that extend downward into the borehole 14, andis connected to a bottomhole assembly (BHA) 20.

The borehole string 12 includes or forms a tubular through which fluid22 is circulated into the borehole 14. In operation, in one embodiment,the fluid 22 is injected into the tubular and/or the borehole string 12by the surface equipment, flows through the tubular and returns to thesurface through an annulus 21 between the borehole string 12 and theborehole wall (or casing if the borehole or borehole section is cased).The fluid 22 may be any type of fluid, such as drilling fluid orstimulation fluid, and may include formation fluid such as water, gasand/or oil that enters the borehole 14.

For example, the surface equipment includes the drilling rig 18 and thefluid 22 includes drilling mud injected into the tubular to facilitate adrilling and/or measurement (e.g. logging while drilling) operations.The BHA 20 includes a drill bit 24, which in this example is driven fromthe surface, but may be driven from downhole (e.g., by a downhole mudmotor). A pumping device 26 may be located at the surface to circulatethe fluid 22 from a mud pit or other fluid source 28 into the borehole14 as the drill bit 24 is rotated.

In the embodiment of FIG. 1 , the system 10 shown is configured toperform a drilling operation, and the borehole string 12 is a drillstring. However, embodiments described herein are not so limited and mayhave any configuration suitable for performing an energy industryoperation that includes a downhole power generator. For example, thesystem 10 may be configured as a stimulation system and/or a completionsystem, which may include components such as a hydraulic fracturingassembly and/or a production assembly (including, e.g., a productionsleeve and a screen).

The system 10 may include one or more of various downhole tools 30configured to perform selected functions downhole such as performingdownhole measurements, facilitating communications, performingstimulation operations and/or performing production operations. Forexample, one or more of the downhole tools 30 may include one or moresensors 32 for performing measurements such as logging while drilling(LWD) or measurement while drilling (MWD) measurements. Other toolsinclude, for example, intelligent production tools, liner setting tools,and tools for logging various information while completing constructionof a borehole.

The system 10 includes a telemetry assembly including a communicationmodule 34 (e.g., a telemetry sub) for communicating with the surfaceand/or other downhole tools or devices. In one embodiment, thecommunication module 34 is configured as a mud pulse telemetry (MPT)device, which includes a pulser assembly 36 that induces pressurefluctuations in the fluid 22. The pressure fluctuations travel as pulsesto a receiver 38 in fluid communication with the borehole 14. The pulsesmay be transmitted with, for example, modulated amplitudes and/orfrequencies, as an encoded pressure signal. The pulser assembly 36includes a valve member 40 that is controllable by an actuator assembly42. Movement of the valve member 40 relative to a fluid passagewayrestriction (not shown) causes changes in differential pressures, whichare transmitted upstream as pressure signals.

The pulser assembly 36 also includes a force balancing assembly 44 thatis configured to counteract forces on the valve member 40 by the fluid22. As discussed in further detail below, the force balancing assembly44 utilizes fluid pressure to apply a balancing force that opposes fluidpressure forces on the valve member 40. The force balancing assembly 44thereby reduces or substantially eliminates fluid pressure sources,which allows the valve member 40 to be moved by the actuator assembly 42using less mechanical power than would otherwise be needed.

One or more downhole components and/or one or more surface componentsmay be in communication with and/or controlled by a processor such as adownhole processor 50 and/or a surface processing unit 52. In oneembodiment, the surface processing unit 52 is configured as a surfacecontrol unit which controls various parameters such as rotary speed,weight-on-bit, fluid flow parameters (e.g., pressure and flow rate) andothers. The surface processing unit 52 (or other processor) can alsoperform monitoring and communication functions (e.g., to gather toolstatus information and information regarding borehole conditions).

The surface processing unit 52 (and/or the downhole processor 50) may beconfigured to perform functions such as controlling drilling andsteering, controlling the flow rate and pressure of borehole fluid,transmitting and receiving data and communications using thecommunication module 34, processing measurement data, and/or monitoringoperations of the system 10. The surface processing unit 52, in oneembodiment, includes an input/output device 54, a processor 56, and adata storage device 58 (e.g., memory, computer-readable media, etc.) forstoring data, models and/or computer programs or software that cause theprocessor to perform aspects of methods and processes described herein.

FIG. 2 illustrates an embodiment of the communication module 34. In thisembodiment, the valve member 40 is configured as a plunger valve memberthat is disposed in a fluid passageway 60. The fluid passageway 60, inone embodiment, is in fluid communication with borehole fluid 22 (e.g.,drilling mud) circulated through the borehole 14. The fluid passageway60 is defined by a housing 62, which can be a bore in a downholecomponent (e.g., a pipe section, drill collar, the BHA 20, etc.) or aseparate housing attached to a component.

The plunger valve member 40 is moveable axially, i.e., in a direction atleast substantially parallel to a longitudinal axis A of the passageway60. The valve member 40 is axially moveable relative to a restriction 64in the housing 62 to generate pressure pulses in the fluid 22. Therestriction 64 may be integral with the housing 62 (e.g., as aprotrusion extending from a wall of the housing 62) or a componentattached to a surface of the housing 62.

To generate a pressure pulse, a controller (e.g., the downhole processor50 or electronics in the communication module 34) causes an actuator toapply a force (referred to as the actuator force F_(A)) and a controlledstroke to move the valve member 40 toward the restriction 64 in thepassageway. By oscillating the valve member 40 according to one or morefrequencies and varying amplitude of the stroke (the amplitude of thedifferential pressure caused by moving the valve member 40) and/orfrequency, the pressure in the fluid 22 upstream the restriction 64 ismodulated accordingly. A series of encoded pulses is emitted to transmitcommunications.

The differential pressure (the difference in pressure between the sideupstream the restriction 64 and the side downstream the restriction 64)produced by movement of the valve member 40 exerts a hydraulic force(referred to as a valve force F_(V)) on the valve member 40. Thecommunication module 34 also includes the force balancing assembly 44,which is configured to counteract hydraulic forces including the valveforce F_(V) on the valve member 40 and thereby reduce the mechanicalpower required to produce pulses. The force balancing assembly 44includes a secondary piston 66 (e.g., a plunger piston) that is exposedto the fluid 22 and to the differential pressure (between the sideupstream the restriction 64 and the side downstream the restriction 64)produced as the valve member 40 moves relative to the restriction 64.The piston 66 is configured to be exposed to the fluid 22 such thatpressure differentials in the passageway 60 between the side upstreamthe restriction 64 and the side downstream the restriction 64 also exerthydraulic force on the piston 66. The hydraulic force on the piston 66is referred to as a piston force F_(P).

A locomotive mechanical transmission assembly 68 is included in thecommunication module 34 to balance forces on the valve member 40. In oneembodiment, the transmission assembly 68 includes a rocker leverbearing, which includes a rocker lever 70 mechanically coupled to abearing 72 that acts as a fulcrum. The rocker lever 70 provides amechanical connection between the valve member 40 and allows balancingof the valve forces. The rocker lever bearing is loaded by the valveforce F_(V) and the piston force F_(P). Through balancing the lever armsand piston surfaces, forces can be efficiently balanced.

The piston 66 is in hydraulic communication with the high pressure sideof the valve arrangement (upstream from the restrictor 64). For example,as shown in FIG. 2 , the piston 66 has a first end 74 in contact (or atleast coupled to transfer force) with an end of the rocker lever 70 anda second end 76 in pressure communication with the fluid upstream fromthe restriction 64. For example, the second end 76 extends through acylindrical opening 78 in the passageway 60.

Whenever the valve member 40 closes and the pressure rises, the piston66 picks up this pressure and thus creates a piston force F_(P) uponthis current pressure. As both the valve force F_(V) and the pistonforce F_(P) have the same direction, they can be connected by a suitabledrive. Accordingly, a force balancing assembly such as the rocker levermechanism reverses direction and force to cancel both forces. Forexample, the rocker lever mechanism transmits the piston force F_(P) tothe valve member 40 and applies the piston force F_(P) to the valvemember 40 in a direction opposite the valve force F_(V). Likewise, therocker lever mechanism transmits the valve force F_(V) to the piston 66and applies the valve force F_(V) to the piston 66 in a directionopposite the piston force F_(P).

Parameters of the piston 66 can be selected or designed to control theamount of force F_(P) on the piston 66. For example, the surface area ofthe end 76 (and the corresponding diameter of the cylinder 78) can beselected to control the amount of force on the piston 66 and thus theamount of balancing.

With valve forces being balanced, the required power to drive the valvemember 40 is significantly reduced. An actuator drive that moves thevalve member 40 would primarily have to account for the inertia loadsand other losses, if correctly balanced hydraulically.

Any of various configurations and mechanisms may be used to affect forcebalancing. In addition to or in place of the rocker lever mechanismdescribed above, the mechanical connection of the force balancingassembly can include rack and pinion gearboxes, crank or cam devices,wobble plates, hydraulic coupling (cylinder piston devices withhydraulic communication) and others.

FIGS. 3-6 show an example of the communication module 34 and anotherexample of a suitable force balancing assembly, employing a rack andpinion gearbox as the mechanical connection. The piston 66 and the valvemember 40 (configured in this example as a plunger valve member) aremoveable axially and guided by a guidance structure 45, such as acylindrical housing or support structure. The guidance structure 45includes respective openings that expose the piston 66 and the valvemember 40 to the fluid 22. The piston 66 is mechanically coupled to afirst actuator rod 80 and the valve member 40 is mechanically coupled toa second actuator rod 82.

Referring to FIG. 4 , the transmission assembly 68 in this exampleincludes rack and pinion drives having a pinion 84, a first rack 86connected to the piston 66 and a second rack 88 connected to the valvemember 40. The rack and pinion drives are selected as a main forcebalancing feature to cancel out the hydraulic forces on the valve member40. The pinion 84 is driven by a bevel gear 90 coupled to an electrical(DC) motor unit 92 (shown in FIG. 3 ). Any suitable gear ratio ortransmission ratio can be used. For example, the transmission assembly68 can have a 1:1 gear ratio or a different gear ratio.

Critical electrical components of the DC motor unit 92 are hydraulicallyseparated from drilling fluid or fluid within the balancing mechanicssection through a separator, such as a rubber bellows 94 or membrane,communicating the pressure and allowing for angular movement. Themembrane or bellows 94 may define a different cavity that can be filledwith a fluid other than the fluid 22 or the fluid within the balancingmechanics section. An independent compensator 96 may be used for thebalancing mechanics section. Since the piston 66 and the valve member 40are mechanically coupled, one of the piston 66 and the valve member 40moves outward while the other moves inward at the same rate (foridentical gear ratio). If both the valve member 40 and the piston 66feature at least substantially identical guidance (or seal) diameter,the internal volume of the balancing mechanics section remains constantduring valve movement, thus limiting or reducing compensator movementupon valve movement. Other suitable combinations of piston 66 (seal)diameter and valve member 40 (seal) diameter can be selected, whilestill allowing the internal volume of the balancing mechanics section toremain constant during valve movement.

In one example, the valve member 40 (seal) diameter is double the piston66 (seal) diameter. This configuration translates into a 4 times largerhydraulic area and thus a 4 times larger volume being displaced inreciprocating movement. In this example, the piston 66 stroke length is4 times the valve member stroke length (and in opposite direction to thepiston stroke) to maintain a constant internal volume of the balancingmechanics section during valve movement, thus limiting or reducingcompensator movement upon valve movement. As can be appreciated, othercombinations can be selected.

FIG. 5 shows the pulser assembly 36 in a closed (pulse) position, andFIG. 6 shows the pulser assembly 36 in an open position. In the openposition, the valve member 40 is located at a first axial position awayfrom the restriction 64 by a selected distance. The distance can beselected based on factors such as fluid flow rate, pressure, desiredpulse amplitude and/or pulse frequency.

In the closed position (also referred to as a pulse position), the valvemember 40 is located at a second axial position proximate to therestriction 64 and closer to the restriction 64 as compared with theopen position. The valve member 40 is shown in FIG. 5 in a fully closedposition and in FIG. 6 in a fully open position. At these positions, thevalve member 40 (in this embodiment a plunger piston or plunger valve)is within the guidance structure (e.g., guidance cylinder) 45, andsealed against the fluid 22. The valve member 40 can be sealed by meansof a narrow gap between the guidance cylinder 45, or by any othersealing mechanism (e.g., o-rings). Since the guidance cylinder 45 andthe seal respectively (as part of the guidance cylinder 45), as well asthe compensator 96, are positioned downstream the restriction 64, theyall communicate to similar pressure levels, hence a small or no pressuredrop across the seal exists, thus increasing durability and life. Thevalve stroke can be adjusted to cover the full flow range of one toolsize. Pulse positions for small flow rates may tend towards smallerdistances between the valve member 40 and the restriction 64 at theclosed position, while at high flow rate the pulse positions may tendtoward larger distances between the valve member 40 and the restriction64 at the closed position and preferably also at larger stroke. Currentflow rates can be measured by suitable devices in the BHA 20, such asturbines or other flow measuring devices known in the industry.

In order to create a signal pulse, the motor driven bevel gear 90rotates some degrees in one direction, while for the opening stroke therotation is reversed. Gear ratios can be adjusted with respect to motortorque capacity and dynamic capacity. With the oscillating movement ofthe actuator, open and closed positions can be individually selectedupon current flow and fluid density of fluid 22 and required signalpressure. Current fluid density can be measured by a downhole device inthe BHA or programmed into a downhole device (e.g., a tool 30) atsurface prior to operation, and/or during operation by means of sendingcommands from surface to downhole (downlink). Downhole fluid densitymeasurements can be performed using the pulser assembly 36, e.g. bydetecting load or other characteristic parameters of the actuator (e.g.the electrical (DC) motor unit 92) at a certain position and flowrate.Other density measurements can be performed by dedicated devices.

Although a rack and pinion device is shown in FIGS. 3-6 , alternativecoupling mechanisms are feasible. Alternative mechanical connectionsinclude rack and pinion gearboxes, crank or cam devices, wobble plates,lever mechanics, and so forth. Mechanics using non-constant transmissionratios for the linear stroke might offer additional advantages.Alternatively, a hydraulic coupling between the valve member 40 and thepiston 66 may be used. In addition, instead of the valve member 40 andthe piston 66 being side by side, they can be positioned concentrically.Furthermore, more than two plunger devices (e.g., more than one valvemember 40 and/or more than one piston 66) can be used. Springs can beadded to balance inertia load or support dynamic movement.

Similar effects can be achieved using a hydraulic system, picking up thehigh pressure upstream the restriction 64 with a cylinder piston deviceand hydraulically supplying the required counterforce to the valvemember 40 by means of a secondary cylinder piston device, mechanicallycoupled to the valve member 40. Hydraulic systems should be designedwith low resistance, which may require large cross sections in thehydraulic communication lines to reduce the losses.

It is noted that, although the force balancing assembly 44 and forcebalancing features are described above in conjunction with a telemetrydevice, they are not so limited. Embodiments described herein can beused in conjunction with other devices and/or systems that are subjectto fluid pressure forces. Examples of such systems include varioushydraulically actuated or operated systems such as sleeves and flowcontrol valves.

FIG. 7 illustrates a method 200 of generating fluid pressure pulses,transmitting encoded pressure signals and communicating by mud pulsetelemetry. The method 200 may be used in conjunction with the system 10,although the method 200 may be utilized in conjunction with any suitabletype of device or system. The method 200 includes one or more stages201-204. In one embodiment, the method 200 includes the execution of allof stages 201-204 in the order described. However, certain stages may beomitted, additional stages may be added, and/or the order of the stagesmay be changed.

In the first stage 201, a tubular such as the drill string 12 isdeployed and the borehole 14 is drilled to a desired location or depth.During drilling, borehole fluid 22 is pumped through the drill string 12and the BHA 20.

In the second stage 202, a downhole component such as the tool 30 and/orthe BHA 20 generates data and/or communication in the form of, e.g., adigital signal. The digital signal is transmitted to the communicationmodule 34. The frequency and stroke length of the pulser assembly 36 isselected for transmission. The stroke length is the difference betweenthe open and closed (pulse) position, and is selected based on thedesired signal pressure and the acceptable pressure restriction in theopen position (the difference between the fluid pressure upstream therestriction 64 when the valve member 40 is at the open position and thefluid pressure upstream when the valve member 40 is at the closedposition). As discussed above, when properly balanced, the actuationforce used to move the valve member does not need to overcome hydraulicforces on the valve member 40 by the pressure differential. Theactuation power is thus limited to other factors such as inertia factors(inertial loads and losses), friction, actuator losses and others.

In the third stage 203, the communication module 34 is operated togenerate pressure pulses in the borehole fluid 22. For example, aprocessing device such as the downhole processor 50, a processor in thecommunication module 34 and/or another processor (e.g., a processor inthe BHA 20 or the tool 30) operates the actuator assembly 42 to generatepulses at selected frequencies and/or amplitudes by varying the positionof the valve member 40 according to the selected stroke length (orlengths).

In the fourth stage 204, the pressure pulses having selected signalpressures and frequencies are transmitted through the borehole fluid 22to another component. For example, the pressure pulses are detected bythe receiver 38 and processed. In one embodiment, a downhole componentand/or the surface equipment 18 includes a telemetry device configuredto transmit pulses downhole. The telemetry device may include a pulserassembly and a force balance assembly as described herein.

FIGS. 8-12 illustrate aspects of operating the communication assembly 34and factors considered in selecting pulse length and other operationalparameters. These aspects are regardless of any balancing mechanism(e.g., as shown in FIG. 2 ) and apply to reciprocating valves ingeneral. As discussed above, to transmit a signal including pressurepulses, the valve member 40 is moved relative to the restriction 64 togenerate pressure differentials that are transmitted upstream as pulses.When moving the valve member 40, the fluid pressure exerts a force F_(V)on the valve member 40 that depends on the relative position of thevalve member 40 to the restriction 64. The position of the valve member40 is denoted as position x, which is an axial distance from therestriction 64 (e.g., a distance in a direction parallel to the axis Aor otherwise parallel to a movement axis of the valve member 40).

FIG. 8 shows an example of the valve force F_(V) on the valve member 40as a function of position x, which corresponds to an axial distancebetween the valve member 40 and the restriction 64. In this example, thevalue of x is zero when the valve member 40 contacts the restriction 64or is at a closest selected position relative to the restriction 64. Therelationship between valve force and position is shown as a valve forcecurve 210. FIG. 9 shows the corresponding fluid pressure differential asa function of the position x, shown as a fluid pressure curve 212.

The open and closed positions may be selected in order to generate aselected signal pressure at a given flowrate. The difference between theopen and closed position used when generating a pressure pulse isreferred to as the stroke length or simply stroke. For example,referring to FIG. 10 , the closed position is selected based on thepressure-position relationship to generate a selected signal pressure(pressure differential). The open position is selected so that thepressure differential at the restriction 64 is relatively low, and thatthe difference between the pressure differential at the open and closedposition corresponds to the selected signal pressure. The low pressuredrop in the open position reduces the erosion of valve components andother mechanical loads.

FIG. 11 shows the valve force F_(V) as a function of position x for theclosed and open positions selected for FIG. 10 . As shown, at an openposition the required valve force would be at a comparably low level,while in a closed position the valve force is at magnitude according tothe required pressure drop from FIG. 10 . Various open and closedpositions can be selected, leading to other forces and strokes.

FIG. 12 depicts the pressure and valve force on the valve member 40 whenusing a smaller stroke length than that shown in FIGS. 10 and 11 , butcreating the same signal pressure. FIG. 12A shows the fluid pressure asa function of the valve position x and FIG. 12B shows the valve forceF_(V) as a function of the valve position. The closed position isselected at a high level of valve force and fluid pressure (e.g., atmaximum permitted pressure with respect to erosion or maximum permittedvalve forces with respect to drive mechanics) as compared to the strokelength of FIGS. 10 and 11 , corresponding to an axial position in closerproximity to the restriction 64. By selecting the closed position at arelatively high level, the same signal pressure as in the previousexample (FIGS. 10 and 11 ) can be achieved with a relatively smallstroke since the exemplary pressure curve within the stroke rate of FIG.12 is changing at a high rate with respect to position.

The actuator may be configured to precisely control the valve memberposition, while at the same time being able to supply a desiredactuation force. Other positions and stroke lengths can be selected toachieve a desired pulse pressure. In general, the closer the closedposition is to the restriction 64, the higher the mean pressure (openand closed pressure) and the higher actuation forces, but the smallerthe required valve stroke. High pressure levels in general have thedisadvantage of creating higher wear and erosion, while operating atsmaller pressure levels demands higher stroke and hence higher dynamicloads inside the actuator.

As noted above, embodiments described herein significantly reduce themechanical power that an actuator must exert to generate pulses havingdesired signal pressures and frequencies. For example, the communicationmodule 34 can achieve the signal pressures without requiring relativelylow power as compared to prior art systems not featuring a balancingassembly (e.g., the balancing assembly 44, thereby requiring less(electrical) power.

FIGS. 13 and 14 demonstrate the significant reduction in actuation forceF_(A) needed to generate desired pressure pulses according toembodiments described herein, as compared to prior art pulsers. In thisexample, the valve member 40 and the piston 66 are connected to thebalancing assembly 44, and the force transmission ratio (e.g., gearratio) of the force balancing assembly 44 is 1:1. FIG. 13 shows a plotof valve force as a function of valve position (curve 214) for a priorart pulser having a pulser assembly similar to the pulser assembly 36but without a force balancing assembly. FIG. 13 also shows a plot ofactuation force (curve 216) using the force balancing assembly 44according to embodiments herein. As shown, the force balancing assembly44 almost entirely balances the valve force, thus creating the values ofcurve 216 as the difference between force of valve member 40 and forceof piston 66.

In some instances, it might be beneficial to not perfectly balance orover-compensate the valve opening force, for example to allow the valvemember 40 to be pushed open by mud flow and without a drive beingactive. FIG. 14 shows a plot of actuation force as a function of valveposition for a balancing piston at a smaller size compared to theexample of FIG. 13 , to maintain an opening force when fluid is flowing.The actuation force of the balancing assembly 44 for positioning of thevalve accordingly in this example is shown by a curve 218.

FIGS. 15 and 16 demonstrate how using a force balancing assembly asdescribed herein can significantly reduce the amount of mechanical powerneeded to drive a pulser. In this example, only the mechanical powerneeded to actuate against the valve force (Power=Valve Force times ValveVelocity) is considered.

FIG. 15 shows the mechanical power required to overcome hydraulic forceson a valve member of a prior art pulser assembly. Curve 220 shows themechanical power required to overcome hydraulic forces as a function oftime during a relatively large stroke, and curve 222 shows themechanical power required for a relatively small stroke.

In this example, a relatively low actuation frequency and a sinusoidalactuation stroke is selected (5 Hz). The benefit of the much smallerstroke leads to reduced power required for the actuation at smallstroke. As mentioned earlier, the high forces and required precision athigh actuator forces might be difficult to achieve.

Since the mechanical power displayed in FIG. 15 is a function of valvevelocity and forces, the power scales proportionally with velocity. Inthe case of sinusoidal movement, the power also scales proportionallywith actuation frequency.

As noted above, other effects (e.g., inertia, friction, actuator losses,etc.) are not considered at this point. Since actuation forces attypical signal pressure levels can be quite high, the mechanical powerdemand to actuate prior art valves can be significant at higheractuation frequencies.

For instance, a demanded signal pressure can be 0.5 MPa, 2 MPa or 5 MPa.Actuation forces for prior art valves can have a respective magnitude of1 kN, 2 kN or 10 kN. Actuation frequencies can range from 0.1 Hz to 100Hz. Power demand at high values can therefore reach several kW.

FIG. 16 shows the required mechanical power for the example of FIG. 15as compared to the required mechanical power using force balancingaccording to the embodiment of FIGS. 3-6 . The mechanical power requiredto overcome hydraulic forces for the large stroke is shown as curve 224,and the mechanical power for the small stroke is shown as curve 226. Asshown, the mechanical power is significantly reduced or almost entirelyeliminated.

Since the mechanical power considered for this example is for simplicitycalculated as a function of valve velocity and forces, the power scalesalso proportionally with actuation force. With balanced forces beingorders of magnitude smaller than valve forces in prior art pulsers, themechanical power can also be orders of magnitude smaller.

Even at high actuation frequencies, with balanced mechanical forces, themechanical power to hydraulically activate the valve member 40 is low,as demonstrated by FIG. 16 . With reduced demand to close the valvemember 40 against the hydraulic force through the balancing mechanism,the required mechanical power and actuation force F_(A) is reduced byfactors or even orders of magnitude, depending on the size of thebalancing piston, making the use of plunger valves feasible for datarate telemetry.

As noted above, with valve forces being balanced by the force balancingassembly, the required power to drive a valve member is significantlyreduced. The actuator drive would primarily have to account for inertialoads and the losses, if correctly balanced hydraulically.

The inertia load can be calculated by deriving the stroke, velocity andacceleration to evaluate required power to overcome inertia losses.

Considering the pressure curve 212 (FIG. 9 ) and the valve force curve210 (FIG. 8 ), selected valve positions (e.g., the open position, closedposition, intermediate positions) and the exemplary design as shown inFIGS. 3 to 6 , valve stroke, valve mass, transmission ratio of rotary(motor) to valve stroke, and rotating inertia can be evaluated andderived from an exemplary mechanical design. The required power tocreate a sinusoidal stroke can be computed therefrom. In the followingexample, only the inertial loads from acceleration of mass and rotatinginertia are considered.

FIG. 17 shows the calculated inertia power requirement (actuation powerneeded to overcome inertia forces) over time for the valve member 40driven according to a 5 Hz sinusoidal movement. The required power for asmall stroke is shown by curve 230, and the required power for a largestroke is shown by curve 232. As shown, valve stroke and hence rotarymovement selected towards smaller values reduces the overall inertialoads, caused by the lower acceleration and velocity of movingcomponents. An optimum case will finally be a negotiation betweenactuator forces (respectively motor torque), erosive wear, controlaccuracy and others.

If carrier frequencies can be adjusted to fixed levels, inertia loadscan be effectively reduced (or cancelled) by added springs. For example,linear springs can be coupled to the valve member 40 and the piston 66,and/or torsional springs can be coupled to a motor shaft, or elsewhere.

While FIG. 17 displays the required power at 5 Hz, other frequencies canbe analyzed. For a sinusoidal valve movement, the curve form remainsidentical, except the amplitude of the power demand scales with thethird power of the actuation frequency—double the frequency causes 8times (2³) the power. For instance, if the maximum amplitude for the 5Hz inertia power requirement according to FIG. 17 is 2 W, the powerdemand at double the frequency would be 2 W×2³=16 W. For 4 times thefrequency (20 Hz) the required power would be 2 W×4³=128 W.

In order to encode signals with appropriate coding technology, valvemovement with higher velocity and acceleration during a pulse cycle maybe desired, as compared to the sinusoidal movement of FIG. 17 . Inaddition, pressure signals can be configured in various ways, and arenot limited to the above examples. For example, the valve member 40 canbe driven to move with different velocities through the low pressurecycle and through the high pressure cycle of the pressure curve.

FIG. 18 shows a pressure curve 234 corresponding to actuation of thevalve member 40 using sinusoidal action and the stroke length shown inFIGS. 10 and 11 .

Shaping the actuation curve allows for creation of a more accurate sinefunction for the pressure signal with less high harmonic content andthus increased signal strength in the carrier frequency. FIG. 19 shows astroke (amplitude) curve 236 representing such an example for a shapedsine actuation with higher velocity through the valve open area andlower velocity during the high pressure time of a stroke. The skewedparts of the curve of FIG. 19 is an example of a signal coding. Forother frequencies, the signal might simply be scaled in time.

In evaluating actuation power demand according to the example of FIG. 19, it should be recognized that, during high acceleration phases(typically occurring when changing phase or frequency for signalcoding), the power required will also be high. FIG. 20 shows an inertiapower demand curve 238 representing the required power to account forrotary acceleration of the rotating components and linear accelerationof reciprocating masses as presented in FIG. 3 .

As shown in FIG. 20 , high peak loads occur during phases of highacceleration. Reduction in stroke, or other measures such as addingsprings, can reduce the power demand. For a more holistic powerassessment the curves for the hydraulic power (FIG. 16 ) and theinertial demand (FIG. 20 ) can be superimposed.

Signals can be encoded using various protocols, such as frequency shiftkeying (FSK), phase shift keying (PSK), amplitude shift keying (ASK).Other examples include more recent coding options such as quadraturephase shift keying (QPSK), quadrature amplitude shift keying (QASK),other time based technologies such as pulse position modulation (PPM),and others.

Set forth below are some embodiments of the foregoing disclosure:

Embodiment 1: A device for generating pressure pulses, the devicecomprising: a valve member disposed in a fluid passageway, the fluidpassageway including a restriction, the valve member movable by anactuator relative to the restriction to generate a pressure pulse in afluid in the fluid passageway based on varying a relative positionbetween the valve member and the restriction and creating a differentialpressure across the fluid passageway, the differential pressure applyinga first force on the valve member; and a piston member in hydrauliccommunication with the differential pressure, the differential pressureapplying a second force on the piston member, the piston member having alocomotive mechanical connection to the valve member.

Embodiment 2: The device of any prior embodiment, wherein the mechanicalconnection is configured to transmit the second force to the valvemember and apply the second force in a direction opposite the firstforce.

Embodiment 3: The device of any prior embodiment, wherein the mechanicalconnection is configured to transmit the first force to the pistonmember and apply the first force in a direction opposite the secondforce.

Embodiment 4: The device of any prior embodiment, wherein the mechanicalconnection is configured to alternately reverse the direction of thefirst force and the second force.

Embodiment 5: The device of any prior embodiment, wherein the mechanicalconnection includes one of: a rocker lever mechanism, a rack and piniongearbox, a crank device, a cam device, a wobble plate, and a hydrauliclinkage.

Embodiment 6: The device of any prior embodiment, wherein the mechanicalconnection has a transmission ratio selected from a ratio of 1:1 and aratio that is different than 1:1.

Embodiment 7: The device of any prior embodiment, wherein a size of thepiston member and a transmission ratio is selected to maintain anopening force when the fluid is flowing through the passageway.

Embodiment 8: The device of any prior embodiment, wherein the actuatorincludes one of: a bevel gear and a crankshaft configured to create alinear motion; a ball screw drive configured to create a linear motion;a direct connection to the pinion driving the rack; and a directconnection to the rocker lever mechanism.

Embodiment 9: The device of any prior embodiment, wherein the actuatorincludes an electric motor and a position feedback device.

Embodiment 10: The device of any prior embodiment, wherein the actuatorincludes a pressure compensator.

Embodiment 11: The device of any prior embodiment, wherein the relativeposition is altered in a manner to create a frequency modulated pressuresignal upstream the passageway with multiple frequencies, wherein atleast one of the multiple frequencies and a phase of the frequencies areshifted for data transmission in the flowing fluid.

Embodiment 12: The device of any prior embodiment, wherein the valvemember is mechanically coupled to a spring.

Embodiment 13: The device of any prior embodiment, wherein the spring isconfigured to create an oscillator with the inertia of movingcomponents, a first natural frequency of the oscillator selected to bein a range of 25% to 200% of one of selected frequencies of a modulatedpressure signal.

Embodiment 14: The device of any prior embodiment, wherein the spring isconfigured to maintain an intermediate stroke position of the valvemember with respect to the passageway

Embodiment 15: The device of any prior embodiment, wherein the valvemember and the piston member are positioned concentrically.

Embodiment 16: The device of any prior embodiment, wherein thelocomotive mechanical connection and the electric motor arehydraulically separated through a membrane, the membrane defining acavity filled with another fluid, the another fluid different than thefluid in the passageway.

Embodiment 17: A method of generating pressure pulses, the methodcomprising: receiving a communication at a processing device, theprocessing device configured to control a communication module includinga valve member and a restriction disposed in a fluid passageway;controlling, by an actuator, movement of the valve member relative tothe restriction to generate pressure pulses in a fluid in the passagewaybased on varying a relative position between the valve member and therestriction and creating a differential pressure across the passageway,the differential pressure applying a first force on the valve member;and transmitting the pressure pulses through the fluid to a receiver,wherein: the communication module includes a piston member in hydrauliccommunication with the differential pressure, the differential pressureapplying a second force on the piston member, the piston member having alocomotive mechanical connection to the valve member.

Embodiment 18: The device of any prior embodiment, wherein themechanical connection is configured to transmit the second force to thevalve member and apply the second force in a direction opposite thefirst force.

Embodiment 19: The method of any prior embodiment, wherein the relativeposition of the valve member is controlled according to at least one ofa flow rate through the passageway and a density of fluid flow throughthe passageway.

Embodiment 20: The method of any prior embodiment, wherein the valvemember is controlled to create pressure pulses, the pressure pulsesconfigured as at least one of: a frequency modulated pressure signalupstream the passageway, an amplitude modulated pressure signal upstreamthe passageway, and a pulse time modulated pressure signal upstream thepassageway.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Further, it should be noted that the terms “first,” “second,”and the like herein do not denote any order, quantity, or importance,but rather are used to distinguish one element from another. Themodifier “about” used in connection with a quantity is inclusive of thestated value and has the meaning dictated by the context (e.g., itincludes the degree of error associated with measurement of theparticular quantity).

The teachings of the present disclosure may be used in a variety of welloperations. These operations may involve using one or more treatmentagents to treat a formation, the fluids resident in a formation, awellbore, and/or equipment in the wellbore, such as production tubing.The treatment agents may be in the form of liquids, gases, solids,semi-solids, and mixtures thereof. Illustrative treatment agentsinclude, but are not limited to, fracturing fluids, acids, steam, water,brine, anti-corrosion agents, cement, permeability modifiers, drillingmuds, emulsifiers, demulsifiers, tracers, flow improvers etc.Illustrative well operations include, but are not limited to, hydraulicfracturing, stimulation, tracer injection, cleaning, acidizing, steaminjection, water flooding, cementing, etc.

While the invention has been described with reference to an exemplaryembodiment or embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the invention.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe claims. Also, in the drawings and the description, there have beendisclosed exemplary embodiments of the invention and, although specificterms may have been employed, they are unless otherwise stated used in ageneric and descriptive sense only and not for purposes of limitation,the scope of the invention therefore not being so limited.

What is claimed is:
 1. A device for generating pressure pulses, thedevice comprising: a valve member disposed in a fluid passageway, thefluid passageway including a restriction, the valve member movable by anactuator relative to the restriction to generate a pressure pulse in afluid in the fluid passageway based on varying a relative positionbetween the valve member and the restriction and creating a differentialpressure across the fluid passageway, the differential pressure applyinga first force on the valve member; and a piston member in hydrauliccommunication with the differential pressure, the differential pressureapplying a second force on the piston member, the piston member having alocomotive connection to the valve member, wherein the actuator includesan electric motor and is configured to apply a third force on the valvemember to generate the pressure pulse.
 2. The device of claim 1, whereinthe locomotive connection is configured to transmit the second force tothe valve member and apply the second force in a direction opposite adirection of the first force.
 3. The device of claim 1, wherein thelocomotive connection is configured to transmit the first force to thepiston member and apply the first force in a direction opposite adirection of the second force.
 4. The device of claim 1, wherein thelocomotive connection is configured to alternately apply the first forcein a direction opposite a direction of the second force and apply thesecond force in a direction opposite a direction of the first force. 5.The device of claim 1, wherein the locomotive connection includes oneof: a rocker lever mechanism, a rack and pinion gearbox, a crank device,a cam device, a wobble plate, and a hydraulic linkage.
 6. The device ofclaim 1, wherein the locomotive connection has a transmission ratio of1:1.
 7. The device of claim 1, wherein a size of the piston member and atransmission ratio of the locomotive connection is selected to maintainan opening force for fluid in the fluid passageway to flow through thefluid passageway.
 8. The device claim 1, wherein the actuator includesone of: a bevel gear; and a ball screw drive.
 9. The device of claim 1,wherein the actuator includes a position feedback device.
 10. The deviceof claim 1, wherein the actuator includes a pressure compensator. 11.The device of claim 1, wherein the pressure pulse includes a frequencymodulated pressure signal in the fluid in the fluid passageway, thefrequency modulated pressure signal having multiple frequencies, whereinthe multiple frequencies are used for data transmission in the fluid inthe fluid passageway.
 12. The device of claim 1, wherein the valvemember is mechanically coupled to a spring.
 13. The device of claim 12,wherein the pressure pulse includes a frequency modulated pressuresignal, the frequency modulated pressure signal having multiplefrequencies, the spring is configured to create an oscillator includingan inertia, a first natural frequency of the oscillator is selected tobe in a range of 25% to 200% of one of the multiple frequencies of thefrequency modulated pressure signal.
 14. The device of claim 12, whereinthe spring is configured to maintain an intermediate stroke position ofthe valve member with respect to the restriction in the fluidpassageway.
 15. The device of claim 1, wherein the locomotive connectionand the electric motor are hydraulically separated through a membrane,the membrane defining a cavity filled with another fluid, the anotherfluid different than the fluid in the fluid passageway.
 16. The deviceof claim 1, further comprising a processor, wherein the processorcausing the actuator to apply the third force on the valve member togenerate the pressure pulse for data transmission in the fluid in thefluid passageway.
 17. The device of claim 1, wherein the actuatorapplies the third force on the locomotive connection.
 18. A device forgenerating pressure pulses, the device comprising: a borehole string ina borehole, the borehole string having a bore defining a fluidpassageway; a fluid circulating though the borehole; a bottom holeassembly in the borehole string including a valve member disposed in thefluid passageway, the fluid passageway including a restriction, thevalve member movable by an actuator relative to the restriction togenerate a pressure pulse in the fluid in the fluid passageway based onvarying a relative position between the valve member and the restrictionand creating a differential pressure across the fluid passageway, thedifferential pressure applying a first force on the valve member; and apiston member in hydraulic communication with the differential pressure,the piston member having an end extending through an opening in thefluid passageway, the differential pressure applying a second force onthe piston member, the piston member having a locomotive connection tothe valve member, wherein all of the fluid circulating through theborehole passes through the restriction and the opening.
 19. A devicefor generating pressure pulses, the device comprising: a valve memberdisposed in a fluid passageway, the fluid passageway including arestriction, the valve member movable by an actuator relative to therestriction to generate a pressure pulse in a fluid in the fluidpassageway based on varying a relative position between the valve memberand the restriction and creating a differential pressure across thefluid passageway, the differential pressure applying a first force onthe valve member; and a piston member in hydraulic communication withthe differential pressure, the differential pressure applying a secondforce on the piston member and moving the piston member in a pistonmember stroke direction, the piston member having a locomotiveconnection to the valve member, wherein the locomotive connection isconfigured to transmit the first force to the piston member and applythe first force to the piston member in a direction opposite a directionof the second force and move the valve member in a valve member strokedirection opposite the piston member stroke direction.
 20. The device ofclaim 19, wherein the locomotive connection is configured to transmitthe second force to the valve member and apply the second force to thevalve member in a direction opposite a direction of the first force.